Studies On Method Of Constructing Core Germplasm Collection And Genetic Diversity Of Boehmeria Nivea

The primary core collection of ramie (Boehmeria Jacq.)was established based on the studies of the technical method, the genetic diversity of the core collection was evaluated on the molecular level.a. Studies on the method of core-collection establishment of ramie:Using different clustering methods, different sampling strategy and different genetic distances of qualitative and quantitative characters to establish core collection of ramie based on the data of25traits of790accessions from the Field Genebank for Ramie(Changsha).6Genetic parameters were used to evaluate the core collections established with different methods. The results showed that different sampling methods have different impacts on qualitative traits and quantitative traits. For the largest genetic diversity of qualitative traits, it is effective to choose stepwise clustering with random sampling strategy and preferred sampling strategy. For the largest genetic diversity of quantitative traits, it is effective to choose stepwise clustering with deviation sampling strategy and preferred sampling strategy. The ramie core collection is the best one constructed by centroid method, single linkage clustering way under stepwise clustering with random sampling strategy and preferred sampling strategy and constructed by ward’s clustering way under stepwise clustering with deviation sampling strategy and preferred sampling strategy. Core collection in ramie was not related with genetic distances of qualitative traits, whereas the core collection of ramie constructed by euclidean distance of quantitative traits was the best.b. Establishing of primary core collection of ramie:The primary core collection of ramie which contained158accessions was established using the method of stepwise clustering with deviation sampling strategy and preferred sampling strategy under20%sampling level. The index of genetic diversity, variance difference percentage and variable rate of coefficient of variation of the core collection were higher than the total collection. The coincidence difference percentage was100%.c. Development of EST-SSR primer for ramie:Different SSR repeats causes changes of the site length which results in SSR Polymorphism. There were76EST_SSR primers designed in the experiment whose SSR repeats were from3to44. Most of them was4repeats (account for30%),3repeats and18repeats account for17.1%of SSRs, respectively. The polymorphic primers of SSR mainly derived from changes in the length of repeat motifs, which ranged froml2bp to44bp. There are mainly12bp and18bp for the length of repeat motifs, accounting for68.4%of EST-SSRs. d. Evaluation of genetic diversity of the core collection by molecular markers:76primer-pairs were tested among62ramie DNA, the PCR products showed that70pairs were effectively amplified. Among the70pairs,50pairs obtained polymorphic PCR bands in which27pairs obtained clear polymorphic bands. The27pairs of SSR primers amplified64polymorphic bands with the average2.37per SSR primer pair in the158cultivars of the core collection. Most of the band varied from80to200bp.SSR technique was used in analyzing the biological genetic diversity of158core collection, and the results showed:the average genetic similarity is0.61, varying from0.27to0.90. The158accessions were grouped into10types based on the cluster analysis. Similarity results were obtained by shortest distance method and chi-square distance based on19field traits.